Initially, I just purchased online, but ordered the wrong part. I called and talked to a real person, who helped me order the correct part and offered a reasonably priced return shipping label. That was a welcome change from other recent online purchase interactions.
Champion Parts
Champion Gardner Denver P05050A Air Compressor Polyester Filter Element PO5050A
Unbranded/Generic
$8.95
Intake Filter Adapter for Champion and Dayton Air Compressors R15 R30 1" FNPT
Unbranded/Generic
$18.95
Valve Tune Up Kit for Champion R10D and R15B Air Compressor Pumps VSTUK-R15B-CH
Unbranded/Generic
$239.95
